Before we get in to the build, here's a before & after so you can really see how this was not a simple plug & play drop in.

It's a Baby AT form factor or non-standard propitiatory design, that's unable to easily accommodate a new mATX motherboard. Massive amounts of cutting, welding, grinding, drilling, thread tapping, and lots of metal filing/deburring will be required.

Originally designed in 1992 and branded as the IBM PS/1. Classic IBM dual layer 16 gauge steel build.

The power supply is mounted low to make way for a rear carrying handle and 3.5" hard drive. This won't allow for a MATX motherboard to fit, so we'll have to lose the handle, and move the power supply up.

This is what it started out with. Proprietary IBM motherboard (Baby AT form factor?)/riser board/power supply.

Stripped, with all redundant proprietary brackets removed, and the back cut out.

Test fit of the new 16 gauge rear panel

Template before making cuts

Tapping threads for the new 6-32 motherboard standoffs.

Standoffs installed.

Wallet ouchy $43 hole saw for 120mm fan and radiator. Ouchy because this hole was the most expensive part of the case build.

I made a bunch of tack welds to avoid overheating the metal and warping it.

Welding complete!

Welds ground down.

Painted satin graphite grey.

While this is drying, lets work on my favorite part of the project, The Floppy SD card reader!

I noticed the 5.25 floppy edge connector had the same spacing a an SD card

I don't have a pic, but with the drive's factory bottom cover on, it's perfectly clean, and undetectable aside from the recessed male USB 3.0 connector.

It's alive!

I decided that I didn't want to mod the factory front bay blanking plates or use cheapo 5.25" bay adapters for IO/card readers, so I incorporated the front audio and an extra USB 3.0 port into the front of the DVD.

Holes cut for the port and jacks. Now the black DVD drive gets some beige treatment.

Came out nice. Not as beige as I wanted, but it works for now.

I took my time, and built my system exactly how I wanted it, with no regrets. It was nasty work at moments, metal shavings and cuts everywhere. Man was it worth it.
Hope you enjoyed viewing this build as much as I did building it. Accomplishment is an awesome feeling.